Sometimes clutter comes from other people's energies that have invaded your space.
When you bring work home, if you've inherited a relative's things, if you're divorced but some of your ex's stuff is with you, if you work from home, if you have kids and they have grown up and moved out but some of their stuff is still there, if you're hanging on to gifts people have given you and you don't care for the gifts, someone else's energies have come into and become a part of your space.
Other people's energies tend to make us feel uncomfortable in our space. We feel like there is less space for us.
I clutter busted with a client who had been taking work home for years. When she spoke of the work papers, folders and files in her space she seemed irritated. The work things felt invasive to her. But she also felt these things had to stay in her home so she could do additional work she couldn't get done at the office. I pointed out how the work stuff was polluting her home and causing her to suffer. She had brought the energy of the entire company she worked for into her living space. I said it would be like a farmer bringing in all the cows from the fields and having them live in his house. She got it that to save her peace of mind, the work stuff had to go back to the office. She needed to maintain her boundaries.
It's important for our well-being that we protect the sovereignty of our space. We can't have that luxury when we're out in the world. But we need it at home so we can rest and recharge.